What can i do for swollen lymph nodes under armpit?

See your doctor: If you haven't already done so, you should see your doctor to determine the best course of action for you.

See a doctor: First thing that needs to be done is to see a doctor to find out why is the lymph node swollen. Further testing like blood tests or imaging studies like an ultrasound will be determined by your physician.

Monitoring Centers: Lymphatic system absorbs/carries things too big to go into the arteries/veins like bacteria eaten by white cells and digested food. Lymph nodes "taste" the lymph for anything bad like bacteria/viruses/cancers, etc. When it detects a problem, it alerts the immune system and your body reacts. They enlarge in response to the inflammation they create when they react. They shrink when all is well.